A hoisting machine of an elevator comprises one or more brakes, which lock the hoisting machine in position when the elevator is stopped at a stopping floor. The brake of a hoisting machine can, in terms of its structure, be e.g. a drum brake or a disc brake. When activating a brake, the activation means, such as thruster springs, press the brake pad of the brake of the hoisting machine into contact with the braking surface on a rotating part of the hoisting machine to brake the movement of the rotating part of the hoisting machine. In normal operation of the elevator, the brake/brakes is/are activated after the electric drive has driven the elevator car to a stopping floor and has stopped the movement of the elevator car. When the elevator is stopped the doors of the elevator car as well as the landing doors on the stopping floor are opened, in which case passengers are able to leave the elevator car and also to move into the elevator car.
From the viewpoint of safe operation of an elevator, it is important that the braking force of the brake/brakes of the hoisting machine is sufficient in total to stop movement of the elevator car in different operating situations, even in a situation in which an overload of approx. 25 percent has been loaded into the elevator car and the elevator car is traveling downwards. One problem is that the braking force might gradually weaken e.g. owing to dirt, grease, et cetera, that has got onto the brake pad or onto the braking surface of the hoisting machine.
Publication WO 2007020325 A2 presents a solution to the problem, wherein the operation of the machinery brakes is monitored by activating the brakes sequentially such that initially only the first brake is activated, and the other brakes are activated with a delay. The operating condition of the first brake is monitored by measuring the movement status of the elevator in a situation in which only the first brake is activated. If it is detected that the operating condition of one or more brakes has deteriorated, the elevator is switched to drive prevention mode. The solution therefore enables regular and automatic monitoring of the operating condition of the brakes.
Although the aforementioned solution does improve the monitoring of the operating condition of the brakes, and thereby promotes the safety of the elevator system, from the viewpoint of elevator service a requirement concerning continuity of the operation of the elevator is also attached to the operation of the elevator. Consequently, it must be possible to return a brake of diminished operating condition to proper operating condition as quickly as possible, because fault situations if prolonged could impair elevator service. It would also be advantageous to find an improvement for minimizing the amount of fault situations of a brake.